The invention relates to photography and photographic equipment and methods and more particularly relates to a dual action shutter release with thumbwheel brake.
Commonly available one-time-use cameras have unexposed film in a prewound film roll. Film is transported during use by means of a thumbwheel or similar advance element that rotates a spool with a film cartridge that receives the film. Perforations along the edge of the film engage and drive a sprocket wheel. A notched cam rotates with the sprocket wheel on a common axle. When a film frame is metered, that is, positioned for exposure, an arm on a film metering lever pivots into the notch of the cam. The same pivotal motion moves another arm of the metering lever into engagement with teeth around the periphery of the thumbwheel preventing further advance to the film until the metered film frame has been exposed. The film is also prevented from backing up by an anti-backup that is biased to ratchet against the thumbwheel teeth. A second cam also rotates with the sprocket wheel. This cam charges a high-energy lever, that is, moves the high-energy lever to a latched position against the biasing of a spring.
An exposure is initiated by depression of a shutter release that releases the latched high-energy lever. The high-energy lever strikes a shutter blade, moving the shutter blade and, thus, opening an exposure aperture and exposing the film. The high-energy lever also pivots the metering lever from the cam notch and releases the thumbwheel and film for advancement. The shutter is closed at the end of the exposure by the action of an additional spring. An example of a one-time-use camera having these features is disclosed in U.S. Pat. No. 5,235,366, issued Aug. 10, 1993.
U.S. Pat. No. 5,614,975 teaches that this kind of mechanism has a risk of film movement during exposure. This is described as being due to energy being stored in the anti-backup mechanism. The energy is released when the metering lever is retracted from the camera notch. The anti-backup then settles between ratchet teeth on the thumbwheel, moving the wheel and the film during the exposure sequence. A solution provided by U.S. Pat. No. 5,614,975 is a brake that engages the thumbwheel when a shutter release is depressed. The shutter release and brake operate only in a downward mode, in which a shutter release button is pushed toward the interior of the camera.
It would thus be desirable to provide an improved shutter release-brake, camera, and method, in which the shutter release is not limited to downward operation, but still includes a thumbwheel brake.
The invention is defined by the claims. The invention, in its broader aspects, provides a camera and a shutter release-thumbwheel brake for the camera, which has a thumbwheel, a shutter release, and a sprag. The shutter release is pivotable relative to the thumbwheel between a ready position and a first released position and also between the ready position and a second released position. The released positions are opposed. The sprag is joined to the shutter release and brakes the thumbwheel when the shutter release is in either of the released positions.
It is an advantageous effect of the invention that an improved shutter release-brake, camera, and method, are provided in which the shutter release can be pivoted in either an upward or a downward direction to release the shutter and to brake the thumbwheel.